I guess my top 5 would be in order:

Shelter
Fire
Water
Navigation
Emotional Control

The first 3 are pretty much self explanitory, build a basic shelter, lean to or pitch a tarp or debris hut. The 2nd, building a fire helps both physically and mentally in a wilderness situation. Water can be important if lost more than a day or so, finding it and purifying it come to mind.

The one that I haven't seen so far that can keep you out of a lot of trouble is different types of navigation, or as I call it, staying found. Compass and map, natural navigation and dead reckoning are becoming lost arts.

The last one, emotional control, I believe CAN be taught to some extent. It is the ability to keep from panicking in a bad situation. So many people make their situation worse by making bad decisions because their emotions. This is one that I am constantly preaching to my son and working on myself.